Southwest desert grasslands are rare ecosystems abundant with biodiversity. Arizona is home to mountains, plains, and desert grasses which used to cover one-quarter of the state. Today, due to historic overgrazing, climate change, and invasive grass, roughly only 30% of native grasses remain in good condition. The remaining grasslands have been invaded by shrubs, invasives, or are now bare ground.
Grasslands are critical for wildlife habitat in a variety of ways. They provide ground cover for rodents, as well as forage for deer and other herbivores. Some native succulent species found is grasslands, such as beargrass (Nolina texana), yucca (Yucca spp), sotol (Dasylirion wheeleri), and agave (Agave spp) provide nectar for insects, birds, and migrating nectar-feeding bats.
The grasslands surrounding Patagonia have changed dramatically over the last 100 years and will continue to change for years to come. Hiking through our grasslands 100 years ago you would not have seen any mesquite trees, except for maybe in a bosque along the riparian corridor. Mesquites, although a native species, found a foothold in grasslands after large-scale overgrazing in the past, by out-competing grasses and rapidly spreading through horse and cow manure.
Native grasses are adapted to our intense summer downpours of southern Arizona. Although this area only receives an average of 18 inches of rain per year, the native grasses are well adapted to the intermittent, heavy rainfall and absorb fast-falling rain, preventing erosion, allowing grasses to thrive and helping the soil to remain intact.
The more than 60 species of grass that thrive in southeastern Arizona are, for the most part, easiest to differentiate in late summer once they flower and start to form seeds. The desert grasses that dominate our wildlands are termed perennial bunchgrasses. This means they grow in dense clusters, or bunches, that come back every spring after being dormant during the winter. They rely on extensive root systems that allow them to dig deep for water and nutrients. The roots of the giant sacaton can extend 20 feet below the ground! Giant sacaton (Sporobolus wrightii) only remains in 5% of its original distribution. You can find it hiking all along the railroad trail heading north out of Patagonia, as well as in the dry lowlands on the outskirts of riparian habitat.
Native grasses to look out for and know in our watershed in order of smallest to largest are: blue grama (Bouteloua gracilis), side-oats grama (Bouteloua curtipendula), cane bluestem (Bothriochloa barbinodis), deergrass (Muhlenbergia rigens) and giant sacaton (Sporobolus wrightii). It’s important to get to know your grasses in our region, both native and non-native. It is a great way to understand the biodiversity in our landscape as well as to support the natives that live in our yards and wild spaces.
The top invasive/non-native species to keep an eye out for are Bermuda grass (Cynodon dactylon), Johnson grass (Sorghum halepense), tumbleweed or Russian thistle (Salsola tragus), which is not a grass but often will take over bare soil in grasslands, and Lehmann’s lovegrass (Eragrostis lehmannii).
A great way to learn your native plants and especially grasses, is to take home a seed head, and look it up. A good source for lists of plants in our region is Jim Koweek’s book, Grassland Plant ID for Everyone, which you can buy online or in numerous local businesses in the Patagonia/Sonoita area or check out at the Patagonia library.
You can also look up native plants through the Borderlands Restoration Network’s catalog on their website (borderlandsrestoration.org) that has lists and pictures, or join your local Arizona Native Plant Society Santa Cruz chapter by signing up at santacruz.aznps@gmail.com